Acceleration-actuated switch



April 15, 1969 J. w. GREEN ET ACCELERATIONACTUATED SWITCH Filed Aug. 18, 1967 FIG.

8 R NC ms: NEL ERU V6 0 wn b 2 K ED u MP n 1 1 1 I W /3 I 5, 0 M 6 l R Y i a 2 0 m H F m m A4 a 2 nnU m m 7/// m M BY 1% @M amw ATTORNEYS 3,439,137 ACCELERATION-ACTUATED SWITCH James W. Green, Scottsdale, and Fred Krahulec, Phoenix, Ariz., assignors to Motorola, Inc., Franklin Park, Ill., a corporation of Illinois Filed Aug. 18, 1967, Ser. No. 661,578 Int. Cl. H01h 35/02, 35/06 US. Cl. 20061.45 5 Claims ABSTRACT OF THE DISCLOSURE An electrical switch having a conductive sphere releasably held between two spring-wire contacts. One of the contacts has a flange extending toward and engaging the conductive sphere. The one contact extends axially in the direction of movement and provides an acceleration threshold for movement of the ball away from the other contact. A third contact may be provided to make a sing1e-pole double-throw acceleration actuated switch.

The invention herein described was made in the course of or under a contract or subcontract thereunder with the Harry Diamond Laboratories of the Department of the Army.

Background of the invention The present invention relates to acceleration actuated electrical switches and particularly to those types which are actuated by impact.

In acceleration actuated devices, which have utilization for many purposes including detonation of armament upon impact, it is desired that the construction be extremely simple yet a reliable acceleration or impact threshold be provided before the switch is actuated or switched to a different electrical state. It is also desired that the acceleration or G threshold be easily achieved and provides a safety-type switch by being in a normally closed position before the G threshold is reached. In an armament situation it is desired to require a setback force from firing howitzer or rifle to permit electrical arming with a reclosing of the switch on impact to fire the armament. Therefore, in armament fuse applications it is desired to have a double-action acceleration responsive switch of small size and reliable operation.

Summary of the invention It is an object of this invention to provide an improved acceleration responsive electrical switch.

It is another object to provide an acceleration responsive electrical switch of simple construction and easy G threshold achievement.

The features of this invention include the provision of a spherical weighty conductive member releasably held by a contact member extending parallel to the direction of accelerations and having a flange extending transversely to such directions to releasably hold a conductive sphere in a first position in response to an acceleration in the first direction and contrariwise to hold it in the second position in response to accelerations in the opposite direction. All accelerations are on the same axis. The member holding the conductor sphere also forms an electrical contact for completing an electrical circuit.

The drawing FIG. 1 is a plan view of an apparatus incorporating the teachings of the present invention.

FIG. 2 is a sectional view taken in the direction of the arrows along line 2--2 as seen in FIGURE 1.

Description of the illustrative embodiment Referring now more particularly to the drawing like numbers indicate like parts and structural features in the United States Patent 0 til 3,439,137 Patented Apr. 15, 1969 two figures. A cup-shaped insulating housing 10 has its opened end closed by contact carrying cover 11 which may have an adhesive bonding material 12 thereon for attaching the switch to a device the acceleration of which is to be used to actuate the switch. Such housing may be considered as being tubular. A weightly conductive sphere 13 is releasably held between the pair of spring or other resilient electrical contacts 14 and 15 fixedly secured to cover 11. As shown, contacts 14 and 15 may be of the ribbon type, no limitation thereto intended. The ends of contacts 14 and 15 may be made arcuate such as to match the curved surface of conductive sphere 13. As best seen in FIGURE 2, spehere 13 is held in a first position between contacts 14 and 15. Axially extending portion 16 of contact 14 yieldably urges sphere 13 against end portion 17 of contact 15. Contact 14 also has transversely extending flange 18 formed on the extreme end of axial portion 16 to engage sphere 13 as shown. Flange 18 may have an arcuately shaped end 19 as shown in dotted line in FIG. 1. It is apparent from the inspection of FIGURES l and 2 that when sphere 13 is in the illustrated position an electrical circuit is completed between contacts 14 and 15 while contact 20 is not connected to either of the contacts 14 or 15 by sphere 13. Upon subjecting the illustrated switch to an acceleration in the direction of the arrow 21, a force in the opposite direction is applied to sphere 13 exceeding the threshold provided by the yieldable urging of portion 16, forces portion 16 to move to the dotted line position 22 in FIG. 2; then sphere 13 is moved axially toward end 23 of cup-shaped housing 10 to assume a new or second position 24, shown in dotted relief in FIGURE 2. Contact 14 remains in dotted line position 22 and an electrical connection is completed between contacts 14 and 20 while the electrical connection between contact 14 and 15 is opened.

Upon the application of an acceleration in the direction opposite to that indicated by arrow 21 in FIG. 2, sphere 13 is subjected to a force urging it to move in the direction of arrow 21. Again upon exceeding the G threshold provided by the resilient axially-extending portion 16, sphere 13 returns to the illustrated position shown in solid lines in FIG. 2. This second oppositelydirected acceleration breaks the electrical circuit between contacts 14 and 20 and remakes the circuit between contacts 14 and 15.

To preset sphere 13 in a predetermined position and to inspect it before subjecting the device to an acceleration axial apertures 25 and 26 are respectively formed in cover 11 and in end portion 23 as best seen in FIG. 2. For example, if the safe or unarmed position of the illustrated switch corresponds to the sphere 13 position indicated by dotted line 24 and the sphere resides in the illustrated solid line position, a rod (not shown) is inserted through aperture 25 to force sphere 13 to the dotted line position 24. To move the sphere in the opposite direction a rod is inserted through aperture 26. The mounting on the device (not shown) the acceleration of which is to be used to actuate the switch and connecting circuits (not shown) determines the initial position of sphere 13.

As shown in FIGURE 2, the G threshold to move sphere 13 from the illustrated solid position to dotted line position 24 would in one constructive embodiment require about 100,000 Gs. To move the sphere from dotted line position 24 back to the illustrated solid line position required only 10,000 Gs. The ratio of G forces of 10 to 1 or greater can prevent accidental actuation of the armament. Therefore it is seen that this switch can provide a different threshold for different actuations in opposing directions. The selection of the threshold is determined by the relative position of the sphere with respect to axially extending portion 16. In the solid line position it may be noted that the flange 18 is well under the center 30 of sphere 13. As a result of this placement a large G force is required to dislodge sphere 13 from the illustrated position. In contradistinction the dotted line position has an engagement between a dotted line 22 and the center of sphere 13 indicated by 30-a which is much closer to the center of the sphere. As a result a much less G-force is required to dislodge sphere 13 from dotted position 24. By moving the center position 30-adownwardly away from flange 18 the reverse acceleration required to move sphere 13 will be increased. In fact, the accelerations in both directions may be made identical, however, for practical applications, the accelerations in the opposite directions are usually desired to be substantially diiterent. Of course the resiliency of portion 16 is a substantial determining factor affecting G force response in both directions.

The contact end portions 17 and 31 respectively on contacts 15 and 20, both act as stop members to the movement of sphere 13. Such contact end portions have no bearing on the G threshold.

Like many acceleration actuated switches the illustrated switch has an integrating factor determined by the relationship of the weight of sphere 13, the resiliency of axially extending portion 16 and the relative position of flange18 with respect to the center of sphere 13, which is also the center of gravity. The selection of the integrating factor can be made according to known design procedures.

Further reliability in operating the acceleration switch is provided by a pair of sphere guides 32 and 33 integrally formed in cup-shaped housing 10. These guides are merely inwardly positioned flat portions of the curved inner surface of insulating housing 10. These guides 32 and 33 are disposed transversely with respect to the contacts 14 and 15 such that sphere 13 is securely held at 4 different points; end portion 17 of contact 15, flange end portion 18 of contact 14 and the transversely spaced apart guides 32, 33. The reliability of the switch is improved by the utilization of these guides in that sphere 13 is prevented from moving around within housing 10 and yet permits relatively wide tolerances in the fabrication of the housing.

We claim:

1. Acceleration responsive apparatus, including in combination,

a tubular insulative housing having first and second end portions and an axis extending therethrough along which acceleration forces are adapted to be imposed,

an electrically conductive sphere having a predetermined mass and movably disposed inside said housing for movement along said axis and having a diameter less than the internal dimensions of said tubular housing,

a first conductive contact member extending axially into said housing from said first end portion and serving as an axial stop for said sphere,

a second conductive contact member inside said housing and including a resilient axially-extending portion having an inwardly radially extending flange releasably engaging said sphere opposite to the engagement between said first member and said sphere and said resilient portion yieldably urging said sphere against said first member and responsive to a force greater than a predetermined threshold acting on said sphere for permitting said sphere to move axially away from said first member past said flange in accordance with said forces,

said housing having a pair of spaced-apart guide means axially extending on opposite sides of said contact members, respectively,-and being in continuous rolling engagement with said sphere for holding the sphere from movement when said resilient portion is urging said sphere against said first contact memher.

2. The apparatus of claim 1 further including stop means in said second end portion for limiting the axial travel of said sphere past said flange to a point such that the center of said sphere is closer to said flange when stopped'by said stop means than when stopped by said first conductive contact means.

3. The apparatus of claim 2 wherein said stop means comprises a second contact.

4. The apparatus of claim 2 wherein said housing has closed ends with said contact members extending therethrough to engage said sphere and further having access means at opposite ends for selectively moving said sphere between said first and second end portions.

5. The apparatus of claim 3 wherein said tubular housing is formed in the shape of a cup and further including a cover closing the open end of said cup housing and said cover fixedly holding said first and second contact members with said axially extending portion extending toward said second end portion for yieldably urging said sphere toward said guides with the guides being transversely disposed on opposite sides of said first contact member.

FOREIGN PATENTS 1,077,761 11/ 1954 France.

RODNEY D. BENNETT, 111., Primary Examiner.

CHARLES E. WANDS, Assistant Examiner. 

